Agent-based modelling (ABM) proves successful as a methodology for the social sciences. To continue bridging the micro-macro link in social simulations and applying ABM in real-world conditions, conventional and often simplified models of decision-making have to be utilized and extended into psychologically plausible models. We demonstrate the contribution of such models to enhance validation and forecasts in social simulations with two examples concerned with sustainable behavior. We start with the Consumat framework to demonstrate the contribution of an established psychological plausible decision-making model in various scenarios of sustainable behavior. Then we use the SiMA-C model to explain how different psychological factors generate social behavior and show how a detailed model of decision-making supports realistic empirical validation and experimentation. A scenario of social media prompting of environmentalfriendly behavior exemplifies the details of how individual decision-making is influenced by the social context. Both examples, Consumat and SiMA-C, emphasize the importance of psychological realism in modelling behavioral dynamics for simulations of sustainable behavior and provide explanations on the psychological level that enable the development of social policies on the individual level.